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Question

I am very...very new to android development and I am trying to recreate a hybrid app I built in ionic, but do it in actual android. I am having an issue with either layouts or fragment loading that I can't figure out. What I want is something similar to the IG layout, where there is a bar at the bottom for navigation, clicking the button would load the new page. From my understanding the best way to accomplish that is to use a main activity, then each of the tabs at the bottom are fragments. So I built that, but I want the top toolbar to disappear on the second tab, so in the second tab "onCreateView" method I added the toolbar.setVisibility(View.GONE); however, as soon as I load the app, even on the first tab, the toolbar at the top is gone, signifying it is loading the views for each fragment when the app loads. I would think that would severely impact performance on a large app. Am I crazy? Here is my main layout for the main activity...

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/main_layout">
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:background="@color/colorPrimary"
        android:elevation="6dp"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
    <android.support.v4.view.ViewPager
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/toolbar" />
    <android.support.design.widget.TabLayout
        android:id="@+id/tab_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabMode="fixed"
        android:gravity="center_horizontal"
        android:layout_gravity="center_horizontal"
        android:background="?attr/colorPrimary"
        android:elevation="6dp"
        app:tabSelectedTextColor="#FFFFFF"
        app:tabTextColor="#D3D3D3"
        app:tabIndicatorColor="#FF00FF"
        android:minHeight="?attr/actionBarSize"
        android:layout_alignParentBottom="true" />
</RelativeLayout>

Then my HomeActivity class..

public class HomeActivity extends BaseActivity implements OnFragmentTouched {

    private TextView mTextMessage;

    private static final String SELECTED_ITEM = "arg_selected_item";
    private int                  mSelectedItem;
    private BottomNavigationView mBottomNav;

    private FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();



    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putInt(SELECTED_ITEM, mSelectedItem);
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onBackPressed() {
        MenuItem homeItem = mBottomNav.getMenu().getItem(0);
        if (mSelectedItem != homeItem.getItemId()) {
            // select home item
            selectFragment(homeItem);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        ViewPager pager = (ViewPager) findViewById(R.id.content);

        PagerAdapter pagerAdapter = (PagerAdapter) new PagerAdapter(getSupportFragmentManager(), HomeActivity.this);

        pager.setAdapter(pagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
        tabLayout.setupWithViewPager(pager);

        for(int i = 0; i < tabLayout.getTabCount(); i++) {
            TabLayout.Tab tab = tabLayout.getTabAt(i);
            tab.setCustomView(pagerAdapter.getTabView(i));
        }
    }

    private void selectFragment(MenuItem item) {
        Fragment frag = null;
        switch(item.getItemId()) {
            case R.id.navigation_home:
                frag = new AllPostsFragment();
                break;
            case R.id.navigation_dashboard:
                frag = ProfileFragment.newInstance(user.getUid());
                break;
            case R.id.navigation_notifications:
                frag = new ChatListFragment();
                break;
        }
        mSelectedItem = item.getItemId();

    }

    @VisibleForTesting
    public ProgressDialog mProgressDialog;

    public void showProgressDialog() {
        if (mProgressDialog == null) {
            mProgressDialog = new ProgressDialog(this);
            mProgressDialog.setMessage(getString(R.string.loading));
            mProgressDialog.setIndeterminate(true);
        }

        mProgressDialog.show();
    }

    public void hideProgressDialog() {
        if (mProgressDialog != null && mProgressDialog.isShowing()) {
            mProgressDialog.dismiss();
        }
    }

    @Override
    public void onStop() {
        super.onStop();
        hideProgressDialog();
    }

    @Override
    public void onFragmentTouched(Fragment fragment, float x, float y) {
        Log.d("FRAGMENT_TOUCHED", "The ChatListFragment touch happened");
        if(fragment instanceof ChatFragment) {
            final ChatFragment theFragment = (ChatFragment) fragment;

            Animator unreveal = theFragment.prepareUnrevealAnimator(x, y);

            unreveal.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) {

                }

                @Override
                public void onAnimationEnd(Animator animation) {
                    getSupportFragmentManager().beginTransaction().remove(theFragment).commit();
                    getSupportFragmentManager().executePendingTransactions();
                }

                @Override
                public void onAnimationCancel(Animator animation) {}
                @Override
                public void onAnimationRepeat(Animator animation) {}
            });
            unreveal.start();
        }
    }


    public String getUid() {
        return FirebaseAuth.getInstance().getCurrentUser().getUid();
    }

    private class PagerAdapter extends FragmentPagerAdapter {

        Context context;

        String tabTitles[] = new String[] {"Home", "Profile", "Chat"};

        public PagerAdapter(FragmentManager fm, Context context) {
            super(fm);
            this.context = context;
        }

        @Override
        public Fragment getItem(int pos) {
            switch(pos) {
                case 0: return new AllPostsFragment();
                case 1: return ProfileFragment.newInstance(user.getUid());
                case 2: return new ChatListFragment();
                default:
                    return new AllPostsFragment();
            }
        }

        @Override
        public int getCount() {
            return tabTitles.length;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return tabTitles[position];
        }

        public View getTabView(int position) {
            View tab = LayoutInflater.from(HomeActivity.this).inflate(R.layout.custom_tab, null);
            TextView tv = (TextView) tab.findViewById(R.id.custom_text);
            tv.setText(tabTitles[position]);
            return tab;
        }

    }

}

So, in the "ProfileFragment" in the onCreateView method I have...

 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_profile, container, false);
        recyclerView = (RecyclerView) rootView.findViewById(R.id.userPostsRecycler);
        RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getContext(), 2);
        recyclerView.setLayoutManager(layoutManager);

        Toolbar toolbar = getActivity().findViewById(R.id.toolbar);
        toolbar.setVisibility(View.GONE);
        followingCountText = rootView.findViewById(R.id.following_count);
        followersCountText = rootView.findViewById(R.id.followers_count);
        titleLayout = rootView.findViewById(R.id.toolbar_layout);

        titleLayout.setTitle(user.getDisplayName());

        fab1Container = rootView.findViewById(R.id.fab_1);
        fab2Container = rootView.findViewById(R.id.fab_2);



        ImageView profilePhoto = (ImageView) rootView.findViewById(R.id.profile_photo);

        Glide.with(this).load(user.getPhotoUrl()).into(profilePhoto);


        fabContainer = (LinearLayout) rootView.findViewById(R.id.fabContainerLayout);
        fab = (FloatingActionButton) rootView.findViewById(R.id.profile_fab);
        instigatingFab = fab;
        fabBaseX = fab.getX();
        fabBaseY = fab.getY();
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showBlurredDialog();
            }
        });

        progressDialog = new ProgressDialog(getContext());

        uploads = new ArrayList<>();

        progressDialog.setMessage("Please wait...");
        progressDialog.show();

        DatabaseReference followersDB = FirebaseDatabase
                .getInstance()
                .getReference("followers")
                .child(user.getUid())
                .child("count");
        followersDB.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                int followersCount = dataSnapshot.getValue(Integer.class);
                followersCountText.setText(Integer.toString(followersCount));
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        DatabaseReference followingReference = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("users");
        followingReference.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        DatabaseReference followingDB = FirebaseDatabase.getInstance().getReference("following").child(user.getUid()).child("count");
        followingDB.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                int followingCount = dataSnapshot.getValue(Integer.class);
                followingCountText.setText(Integer.toString(followingCount));
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        mDatabase = FirebaseDatabase.getInstance().getReference("/userPosts").child(user.getUid()).child("posts");

        mDatabase.limitToFirst(25).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                progressDialog.dismiss();

                for(DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                    String postID = postSnapshot.getKey();
                    uploads.add(postID);
                }
                uploads.add("-KtvzkOL_75wiKA4CMsr");


                adapter = new ProfileUserPostsViewHolder(getContext(), uploads);

                recyclerView.setAdapter(adapter);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                progressDialog.dismiss();
            }
        });
        return rootView;
    }

As you can see I am setting the visibility for the toolbar from the HomeActivity to View.GONE, however, the toolbar is gone from all fragments now. I just want a bottom navigation setup with a top toolbar that can be hidden when certain fragments load, but is visible in other fragments. Is that even possible? Thank you.

Answer 1

You can control the numbers of fragments loading in view pager by simply using this method:

  viewPager.setOffscreenPageLimit(1); // where n is the number of offscreen pages you want to load.

you can increase or decrease the number of fragments loading according to your requirements but atleast 1.

hope this will help you.